1. Field Of The Invention
The present invention relates to electrical connector assemblies and particularly to a user configurable connector assembly capable of being formed as a semi-finished product for inventory. The connector assembly later can be configured to the specific design requirements of a customer by the simple insertion of desired filter components, conductive members and associated contacts into selected passageways. The connector assembly includes an integrated filter component for filtering or suppressing the effects of electromagnetic interference or high frequency and radio frequency interference.
2. The Prior Art
Electromagnetic interference or high frequency and radio frequency signals are often radiated or conducted to susceptible electronic equipment and interfere with the performance of that equipment. Electromagnetic interference sources include sparks, lightning, radar, radio and TV transmission signals, brush motors and line transients. Additionally, a spark from a static discharge often is a source of electromagnetic interference.
By means of line conduction or even by propagation through the air, electromagnetic interference may induce undesirable voltage signals in electronic equipment. Such interference is especially prevalent at connection devices. The effects of electromagnetic interference may vary from mere static on a car radio, to a malfunction of an aircraft navigational system. Electromagnetic or high frequency interference may even result in incorrect readouts on sensitive medical diagnostic equipment.
Accordingly, it is extremely important to mitigate or to substantially eliminate the effects of electromagnetic or high frequency interference on a wide variety of instruments.
Due to the multitude of sensitive electronic devices that may be adversely affected by electromagnetic or high frequency interference, there is an increasing need for electrical connectors that provide good filtering capability over a wide range of conditions and uses. There is also a need for an electrical connector which may be user configurable in order to adapt to a wide variety of interfaces for connecting together different electrical devices with a minimum of interference.
What is also needed is a filtering connector capable of being formed as a semi-finished product to be stored as inventory by a manufacturer. This would enable, at a later time, large numbers of contacts to be assembled with desired filter components so that the connectors may be quickly and simply adapted for a particular use in a wide variety of electrical devices in accordance with a customer's instructions.
With regard to filtered connector assemblies, the prior art is characterized by basically four types. The first type of filtered electrical connector employs a monolithic planar capacitor for engaging each electrical contact axially. Examples of this type of electrical connector would include the following: U.S. Pat. No. 4,376,992, U.S. Pat. No. 4,589,720, U.S. Pat. No. 4,653,838, or U.S. Pat. No. 4,710,710.
A second type of electrical connector is characterized by a series of axial contacts and corresponding apertures for coupling the contacts. Each aperture has a capacitor attached around its circumference. The axial contact is inserted through the capacitor. An improvement of this prior art type employs a tubular sleeve capacitor for receiving electrical contact. Examples of this type of filter would include U.S. Pat. No. 3,710,285, U.S. Pat. No. 3,764,943, U.S. Pat. No. 4,020,430, U.S. Pat. No. 4,215,326, U.S. Pat. No. 4,222,626, U.S. Pat. No. 4,265,506, U.S. Pat. No. 4,296,389, U.S. Pat. No. 4,679,013, or U.S. Pat. No. 4,846,732.
A third type of prior art filtered electrical connector uses a "chip" type capacitor to couple with the contact. Examples of this type would include U.S. Pat. No. 4,500,159, U.S. Pat. No. 4,804,332, or U.S. Pat. No. 4,880,397.
A fourth type of filtered electrical connector of the prior art utilizes a so called "array" type capacitor which provides a planar filter associated with a series of corresponding axial contacts.
There are significant disadvantages associated with prior art filtering electrical connectors. For example, the "array" filters are expensive and somewhat complicated to manufacture. The "feed through" filters using tubular capacitors suffer from problems of strain and deformation due to vibration and applied compressive forces. Because the capacitor contacts must be individually soldered or bonded to a conductive plate, this increases the expense of assembly. The tubular type capacitors also are subject to breakdown due to their fragility and are therefore unsuitable for use in harsh operating environments, such as in motor vehicles, aircraft, or the like, where components will be subject to extreme temperature and vibration. As to the monolithic planar filters, these are also subject to similar limitations due to their relatively delicate structures.
For the above reasons, the present invention adopts the "chip" type or integrated filter component. Chip type filter components are inexpensive compared to other types of filters, and also possess a more rugged structure.
There are two basic kinds of prior art connectors employing chip type filter components. Examples of these types are illustrated by U.S. Pat. No. 4,500,159 and U.S. Pat. No. 4,804,332. In both patents, a series of cavities are disposed above and transversely to the axis of the contact. Chip capacitors or other chip components are then disposed in each cavity from above. Each chip directly touches an associated contact at a right angle. Thus, each capacitor has a direct contacting relation with the contact. This can result in damage to the capacitor if the contact is inserted roughly into the cavity. The direct connection between the contact and the capacitor disposed in a transverse relation may also result in the direct transmission of torsional forces or rotational movement from the contact to the capacitor. This can damage the electrode of the capacitor, or can degrade or destroy entirely the continuity of the electrical contact between the capacitor and the contact.
The prior art has the additional disadvantage that the chip capacitors must be permanently placed into the internal portion of the connector before final assembly so that the connector will be functional. Thus, in the prior art, it is not possible to manufacture the connector assembly as a semi-finished product and later insert components to configure the finished product in accordance with a customer's design specifications. For example, in U.S. Pat. No. 4,500,159 all the chip capacitors are assembled in a row of cavities in a bus bar. A discrete capacitor is placed in each cavity and in direct communication with the contact, the contact being a pin, socket or the like. In addition, a one-piece spring member includes a plurality of spring tines, each having a portion disposed in a cavity for holding the chip capacitor in an electrically contacting relation with the contact. The one-piece spring member presses all the capacitors into a direct contacting relation with the contact. The one-piece spring member also provides the function of ground the capacitors as well as maintaining them in electrical communication with the contact. This is disadvantageous because prior to final assembly of the electrical connector, each chip capacitor must be in place in a respective cavity. This limits the connectors to a few predetermined shapes and completely eliminates the possibility of user configurability in accordance with each customer's own design specifications.
U.S. Pat. No. 4,804,332 also provides a row of chip receiving cavities in a bus bar. The cavities are also arranged transversely to the axis of the terminal contact. A contacting member must communicate with the contact and with each capacitor or chip-type component individually. Further, each capacitor is preferably soldered or otherwise fixedly bonded in its respective cavity. This also has the disadvantage that the connector configuration is inherently inflexible. The capacitors must be configured as a single row in a bus bar. Additionally, an entire row of capacitors must be inserted at the same time into the bus bar and soldered, welded or otherwise fixedly bonded within the cavities. This precludes a flexible manufacturing system which would enable each connector to be customized or configured in accordance with the user's unique design. Because the prior art fixes the capacitors in a predetermined configuration into the internal portions of the connector assembly prior to final assembly of the connector, it is impossible to thereafter alter the configuration in order to conform to a customer's exact requirements.
This is a serious disadvantage in the prior art, because a customer such as a computer manufacturer, must be forced to use an inappropriate connector configuration or be forced to modify its own design specifications in order to conform to an available connector assembly. This is a wasteful practice and results in connectors which are not adequately suited to the customer's design specifications for the needs of the system and accordingly do not perform filtering functions as adequately as they should.
The prior art devices also have the disadvantage that the manufacturer of the electrical connectors must receive instructions from the customer before the product can be fabricated and assembled. This disadvantageously results in a long lead time with respect to the customer. Any delay in manufacturing of the connector assemblies can severely upset the predetermined schedule of the customer if the connectors are to be a component of the final product, such as a computer.
Another problem results when the manufacturer of electrical connectors must fabricate and store large numbers of filter connectors having many types of configurations and differing design requirements in order to be prepared to meet the needs of the customers. While this can avoid the disadvantage of a long lead time, it nevertheless results in problems in keeping track of a large inventory and may also result in a considerable amount of frozen capital investment.
Therefore, in the prior art, many different filter components must be permanently bonded to contacts or otherwise assembled as a finished product or held in storage in order to anticipate the needs of a customer. This results in the added expense of keeping large quantities of filter connector components or a great variety of electrical connectors in inventory in order to meet a customer's anticipated demand. Also, a customer often may be forced to use an electrical filter which merely approximates its needs and thus adversely affects the function and cost of an entire apparatus.
In the prior art, an electromagnetic shield is generally provided by a screen or other conductive housing placed around devices or circuits to reduce the effects of both electric and magnetic fields on the devices being connected. The electromagnetic fields result from the presence of a rapidly changing electric field and its associated magnetic field. Shielding from the electromagnetic interference is a combination of reflection and absorption of electromagnetic energy by the material. Reflection occurs at the surface of the material much like the reflection of light at an air-to-water interface, and is not usually affected by shield thickness. Absorption, however, occurs within the shield and is highly dependent upon thickness.
Another disadvantage inherent in prior art connector devices is the failure to minimize distances between a filtering means such as a capacitor and the connection between the terminal contact and ground. This increases the probability of stray inductances and renders many prior art filter connectors completely unsuitable for use in precision electrical instruments. Prior art devices also suffer from a failure to maximize the area connecting complete ground with the terminal contact and the filtering device.